Steam-boiler.



J M. CAMERON.

STEAM ,BOILER.

12111101111011 FILED APR.19, 1911.

1,018,8781 Patented Feb. 27, 1912.

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COLUMBIA PLANOURAPH co., WASHINGTON, D. c.

J. M. CAMERON.

STEAM BOILER. APPLICATION IILED APR. 19, 1911.

Patented Feb. 27, 1912.

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JOHN M. CAMERON, OF JOHNSON CITY, TENNESSEE.

STEAM-BOILER.

To all whom it may concern:

Be it known that 1, JOHN M. CAMERON, citizen of the United States,residing at Johnson City, in the county of WVashington and State ofTennessee, have invented certain new and useful Improvements in Steam-Boilers, of which the following is a specification.

My invention relates to steam boilers and particularly to fire tubeboilers of the type illustrated and described in Patent No. 9145417,granted to William J. Ellis on the 9th day of March, 1909. Boilers ofthis type are crescent shaped in section above the fire box, and nearlyinclose a central flue, by which the products of combustion are carriedback to a combustion chamber. From the combustion chamber the productsof combustion are carried through the boiler by means of return tubesopening into a smoke box at the front end of the boiler from whichextends an uptake. Goal is supplied to a hopper or reservoir on eachside of the boiler shell and falls to the grate by gravity. The fine isformed by the reentrantly curved bottom of the boiler.

In designing a boiler to meet present day requirements, it is necessarythat strength be provided to carry with safety the pressure desired;that the boiler be proof against explosion; that the parts be soarranged that the internal surface can be examined by sight and beaccessible for the removal of mud, scale and other accunnilations, thatre pairs can. be made to the tubes, rivets, braces, etc, withoutdisturbing the setting, that the several parts of the boiler be free toexpand and contract with changes of temperature without buckling theboiler shell or flue and without undue shearing strain on the rivets,and that the free and natural circulation or movement of the waterwithin the boiler be unobstructed by braces, stay bolts, plates, etc,crossing the line of flow.

The crescent shaped type of boiler referred to above does not meet therequirements above set forth, for the reason that pressure within theboiler tends to expand the legs of the boiler or cusps of the crescentso that they spread, and the primary object of my invention is toeliminate this defect by providing a system of internal bracing which,while giving the boiler a maximum of strength, does not act to obstructthe natural movement of the water in the boiler, this in- Specificationof Letters Patent.

arrange and construct the tie plates, tie bars and other members actingto brace the boiler, that the legs of the boiler may be easily cleanedand the condition of the inner surface at the bottom of these legs maybe easily observed.

Other objects will appear in the course of the following description.

My invention is illustrated in the acco1npanying drawings wherein:

Figure 1 is a longitudinal vertical section on the line 1-1 of Fig. 3.Fig. 2 is a longitudinal horizontal section onithe line 22 of Fig. 1.Fig. 3 is a transverse vertical section on the line 3-3 of Fig. 1. Fig.at is an end view of the boiler and furnace. Fig. 5 is a detailsectional view of one of the bolts and nuts 17 for holding the tie bar16 in place. Fig. 6 is a diagrammatic sectional view of a circularboiler. Fig. 7 is a diagrammatic sectional View of a crescent shapedboiler. Fig. 8 is a diagrammatic sectional view of a crescent shapedboiler showing the forces acting on the boiler and showing in dottedlines the position taken by the different elements of the boiler underpressure. Fig. 9 is a perspective view of a U-shaped element. Fig. 10 isa perspective view of a like U- shaped element strengthened bytransverse tie plates.

Corresponding and like parts are referred to in the followingdescription and indicated in all the views of the accompanying drawingsby the same reference characters.

In order to illustrate the action of my internal bracing, I will referfirst to the diagrams, Figs. 6 to 10. In Fig. 6 there is illustrated infull lines a cylindrical boiler shell which offers a maximum ofresistance to either external or internal uniform pressure. Such a shellas this requires no bracing, but if the lower portion of the boiler beflattened or formed as shown by the dotted lines in Fig. 6, pressurewithin the shell Will force the flat bottom Z down until the wholeperiphery is a true circle. This circle will have a diameter less thanthe original diameter of the shell and in pressing down bottom Z, thesides A and B will be forced in against the pressure, in the directionPatented Feb. 27, 1912.

Application filed April 19, 1911. Serial No. 622,150.

' nation.

shown by the arrows. Inasmuch then as the pressure on the sides A and Bacts to keep the bottom Z flat and under tension, and the pressurevertically downward acts to force the portion Z out of its flatposition, it follows that a suspension brace from the point X to Z inorder to support the flattened portion Z against strain would require astrength equal to the difference between the strength of the twoopposing forces. Vhere a crescent shaped boiler is to be braced,however, an entirely different solution is required. The boiler shell atX might be connected to the top of flue Q, at the point Z by asuspension brace of unlimited strength, and unless the gap Y be bridgedby a tie bar S, the boiler shell will be forced to assume a formdifferent fronithat shown. The internal pressure on every square inch ofsurface in a boiler having the shape of that shown in Fig. 7 acts towiden the gap between the two legs of the boiler and cause a change ofform which is detrimental to the safety of the boiler. The flue passageQ in the bottom of the boiler in this type of boiler extends the fulllength of the furnace, and tie rods S can be placed only at each end ofthis opening. It is necessary then to provide means whereby the pressureacting to force the boiler shell out of normal correct shape shall beresisted throughout that part directly over the fire.

In Fig. 8 a boiler shell is shown having the same form as that in Fig.7, but having tie plates M securely riveted to the boiler shell and tothe flue. The horizontal force acting to widen the gap Y between the twolegs of the boiler may be symbolized by the levers N, O, P. Each of thelevers N, O, P is a lever of the third class with a fulcrum at N. Thepower at O combines with the downward pressure on a surface equal to thehorizontal diameter of the boiler shell, multiplied by the length of theinverted flue, to force the boiler shell to a shape shown by the dottedlines in Fig. 8. This will be understood better with the followingexpla- Assume that the curved surface of the boiler shell from the pointX to the point E is of infinite strength against bending. Assume thatthe halves of the shell are hinged together as at X and that the lowerpart of the shell is connected to the inverted flue Q as shown formingthe cusps of the crescent.

' infinite strengthagainst bending and that it Assume that the invertedflue has verted flue are considered as-being hinged at the points X andZ, it will be clear that the pressure within the boiler over the wholearea mentioned acts to widen the gap Y by pushing upward against the topof the' boiler shell, and pushing downward against the inverted flue andthe lower portion of the boiler shell. Now to prevent the inverted fluefrom being forced down, suspension braces are put in. These suspensionbraces and the boiler shell act against any downwardly acting pressure.

In considering the pressure acting horizontally, and remembering that itis assumed that the curved boiler shell and the inverted flue haveinfinite strength, it is clear that the internal pressure at EE actingto force the boiler shell out is neu tralized by the internal pressureacting to force the inverted flue in, so that the pressure within thecusps of the crescent-shaped shell does not tend to widen the gap Y.This, however, is not the case with the pressure above the invertedflue.

To make the action of the pressure above the inverted flue clearer, wewill assume that the boiler is rectangular in form, this rectangle beingbounded by the line NN, the lines AB and the lines CD. Each side of theboiler will present a plane having a vertical distance XZ, and a lengthequal to that of the inverted flue, and on the sur- 7 face of this planethe pressure will act uniformly in a horizontal direction. Inasmuch asthe top of the plane is securely fastened to the upper sheet of theboiler, we have the leverage as shown'in Fig. 8, in' which the lever N OP represents the vertical distance from X to the cusps of the acrescent. The pressure acting horizontally against the vertical planeC-B or D-A is assumed to be concentrated ona line through the center ofthis plane as at O, andthe force tending to widen the gap Y will be thepressure on the plane CB for instance multipled by the distance N-O anddivided by the distance N-P. I

Assuming that the boiler has been allowed to take the form shown inthedotted lines in Fig. 8, a comparison of the distances I in theunexpanded boiler with the distances I in the expanded boiler will showthat the lower part of the plate M has been under compressive strain,while the upper part of the plate M has been placed under tensilestrain, the last being shown by a comparison of the distances I betweenthe expanded and unexpanded boiler. The change in shape:of plate i I,however, is so slight in comparison with the movement of the flue andlower part of the boiler shell, that'these plates in'thfemselves havebut little value in preventing the widening of gap '1 by the force ofpressure within the boiler. Supporting rods from X to Z will also notprevent the widening of the gap Y, as has been before explained.

Keeping in mind that the force within the boiler is acting in twodirections to change the shape of the shell, namely, vertically asindicated by the arrows X, Z, and horizontally as indicated by thearrows on line OO, it is evident that strength to withstand these forcesmight be had by stay bolts or tie rods radially placed from the flue tothe boiler shell, but in a high pressure boiler the number of such rodsor stays woulgl have to be so great that little room would be left forthe boiler tubes, and the tubes instead of being placed in horizontaland vertical rows, as required by good practics, in order that all partsof the boiler may be examined and cleaned would have to be placedirregularly in staggered rela tion, and as the stay bolts or rods wouldcross the line of direction of the natural flow of the water at everyconceivable angle, they would greatly retard the water circulation andthus reduce the efficiency of the boiler. The simplest means forpreventing the widening of gap Y bet-ween the two cusps of the crescentshaped boiler is a tie bar or its equivalent disposed at each end of thegap Y, this tie bar being indicated by the letter S in the diagram Fig.7.

We will now assume that the boiler shell is supported by members S aswell as tied together thereby, and we will assume that the pressureacting downwardly on a horizontal plane extending through the center ofthe boiler to be considered as concentrated at EE. Fig. 9 is a diagramillustrating the action of the trough shaped bottom of a boiler leg. ewill consider this trough shaped portion illustrated in Fig. 9 as a beamuniformly loaded throughout its length, the sides T-T being unsupported.The neutral axis of the beam is on the line UU. The bottom of the troughbeing'under tension and the upper part of the side plates T being undercompressive strain, the plates T which are relatively thin and arerelatively of great length will easily bend under strain, and thedistance from the bottom, or'that part of the plate which is undertensile strain, to the neutral axis being small, the strength of themember illus trated in Fig. 9 is proportionately low. In Fig. 10 I showthe same trough shaped member having the sides TT, but fitted with thetie plates M previously referred to and illustrated in Fig. 8. These tieplates being securely riveted to the sides "-T transform the relativelyweak beam shown in Fig. 9 into a beam of great strength as illustratedin Fig. 10, the tie plates prevent ing any bending of the sides T-T whenunder compressive strain. The neutral axis is raised by the tie platesto line VV, and as the strength of the element considered as a beamvaries with the distance of the neutral axis from the bot-tom of thebeam, it is clear that the tie plates M have great value as astrengthening means when the structure is considered as a beam uniformlyloaded. It will be seen then that by providing the cusps of the crescentor the lower ends of the water legs with the transversely extending tieplates M as in Fig. 8, I secure great strength for the boiler whenconsidered as a beam uniformly loaded, andthat if the uppersurface ofthe flue Q be secured to the roof of the boiler by suspension rodsparallel to the line X, Z, these, in conjunction wit-h the plates M andthe plates forming the boiler shell and flue, will give any requiredstrength to carry pressure acting vertically. We now come to aconsideration of the force acting to widen the gap Y through the leversN, O, I. We will assume that the legs of the boiler are tied by the tiemember S and will consider the boiler as rigidly supported at each end.Referring again to Fig. 10, we will assume that the element showntherein is acted upon by the weight IV and that the element is nowrequired to carry a uniformly distributed load acting in a horizontalplane as indicated by the pull of the weight WV. Under thesecircumstances, the element may be considered as a bridge truss rigidlysecured at each end. The tie plates M will now form struts and by addingdiagonal braces or trusses between the tie plates, as illustrated inFig. 2, any desired strength is secured.

A boiler of the form shown in Fig. 7 without the tie bar S and withoutinternal bracing of any kind will sustain a low internal pressure persquare inch. If the tie plates M are fitted in place in the legs of theboiler, the strength of the boiler will be increased and a higherpressure may be safely allowed. If the top of the flue Q be supported byrods attached to the roof or crown of the boiler, the strength is againincreased, allowing a further increase of pressure in the boiler. Byadding the tie bar S, the strength of the boiler is again greatlyincreased and by fitting diagonal braces between the plates M, astrength and stiffness is secured that will carry any reasonablepressure.

In Figs. 1, 2, 3 and 4, I show a boiler of the type before referred towhich is internally braced in accordance with the principles beforestated. The boiler 1 is crescent shaped in cross section. The spacebetween the cusps of the crescent forming a U-shaped flue 2 open at itsbottom into a furnace 3 which extends the entire length of the flue 2.At the rear of the furnace the inverted open bottomed flue 2 becomescylindrical as at 5 and extends rearward through the boiler to acombustion chamber 6 formed upon or attached to the rear end of theboiler. The products of combustion pass from the combustion chamber 6through return tubes 7 to a smoke box 8 located at the front end of theboiler. The inverted open bottomed flue 2, the cylindrical continuation5 thereof and the combustion chamber 6 are each lined with fire tile 9to protect the plates and rivets from intense heat and to assist insecuring a more perfect combustion of fuel than would be possible werethe hot gases allowed to come in contact with the relatively coolsurface of the shell before the combustion was completed. In order tosupply airfor perfect combustion, I provide an air inlet 10 in thebridge wall 10, but the particular manner. whereby cold air is appliedto the combustion chamber does not form any part of the presentinvention and therefore need not be particularly described.

In order to secure the boiler strength necessary to carry a highpressure, that portion of the boiler shell which forms the U- shapedflue 2 is strengthened against collapsing under pressure by angle irons11. These are each arcuate in form and are closely riveted to the plateforming the bottom of the boiler and the wall of the flue 2, and extendover half of the flue circumference. Extending between the boiler shelland the angle iron stiifeners are the tie plates 12 which correspond tothe plates M in Fig. 8. The ends of these tie plates are flanged as at13 and the plates are securely riveted in a plane perpendicularto theaxis of the boiler. As shown in Fig. 3, these plates 12 are located inthe cusps of the crescent shaped boiler but do not extend down to theextremities of the cusps.

Securely riveted to the plates 12 are the diagonal braces let, the outerends of these braces being riveted to the next adjacent tie plate 12.These diagonal braces act as trusses resisting any lateral strain.Suspension rods 15 are attached at their upper ends to the boiler shellas illustrated in Fig. 3, and at'theirlower ends are attached to theangle iron stiffeners 11. These suspension rods 15 'act to prevent theflattening of the flue sheet in a manner previously described. The.boiler shell proper, that portion of the boiler shell which forms theflue sheet, the angle iron stifleners 11, the tie plates 12 and thesuspension rods 15 are intended to carry with safety any pressuredesired; the

,whole construction being considered as a vented from expansion by meansof a tiebar 16 held in place by bolts 17, the rear 'end of the flue 2being securely riveted to the cylet 18, safety valve outlet 19, blow-offoutlet 20, clean-out plug 21 and manhole 22. The combustion chamber isprovided with an opening closed by a plug 23 and the combustion chamberis formed with a clean-out opening 2%. The boiler may be supported inany convenient manner over any ordinary type of furnace and I have notattempted to show any detailed construction for the furnace but show thedoors thereof.

It is to be particularly noted that the tie plates 12 do not extend tothe bottom of the boiler. It is at this point that the fierce heat ofthe furnace impinges against the boiler, and it is most important thatthere be no obstruction to the free passage of the water over the plateat this point. The rapid transmission of heat causes a swift flow of thewater and prevents the deposit of mud, sediment or scale at thesepoints. As the boiler is inclined toward the rear end in setting, themud and other foreign material is carried to the rear where a blow-offconnection 20 is provided. The space between the tie plates 12 permitsthe free vertical circulation of water.

In order that the condition of the boiler sheet may be observedparticularly at the points 25,1 prefer to secure the tie bar 16 to theboiler head by large removable bolts 17. Each of these bolts is tubularas illustrated in the detailed view, Fig. 5, and the tubular boltisfitted with a plug 26 which can be removed, allowing a pipe or hose tobe inserted for washing out the boiler. By holding a light in theclean-out opening 21 and looking through the tubular bolt 17, thecondition of the internal surface can be seen.

If necessary to clean the internal surface of the boiler sheet withscrapers, the tie bar 16 and the bolts 17 are removed and the cleaningcan then be readily accomplished by the openings provided for the bolts.Inasmuch as the only portion of the boiler liable to be damaged by heatis the plate surface at 25, and as all the bracing and strengtheningplates are above the points 25, it follows that while a rupture mightoccur at 25, an explosion due to weakening of the plates overthe furnaceis impossible.

lVhile I do not wish to limit myself to any particular method or mannerof heating this boiler, it may be stated that with this type of boilerthe boileris Set within a U-shaped casing designated 26 in the drawingwhich forms a coal hopper. This casing has the same length as the firebox and delivers the coal onto the grate bars 4. The coal is coked as itpasses downward. through the legs of the hopper 26 and burns upon thegrate bars immediately beneath the opening of the flue 2. I have notillustrated any means for feeding the coal, regulating means forinternally strengthening the boiler itself.

What I claim is:

1. A boiler crescent shaped in cross section and having a reentrantbottom forming an inverted U-shaped fine, and tie plates between theree'ntrant bottom and the outer shell of the boiler.

2. A boiler crescent shaped in cross section to form opposedlongitudinally extending water legs and having a reentrant bottomforming an inverted U-shaped flue, and tie plates extendingperpendicularly to the axis of the boiler and disposed in the waterlegs, the lower edges of said tie plates being above the lower ends ofthe water legs, said tie plates being attached at their outer ends tothe exterior shell of the boiler and at their inner ends to the bottomof the boiler forming the flue.

3. A boiler crescent shaped in cross section to form opposedlongitudinally extending water legs and having a reentrant bottomforming an inverted U-shaped flue, tie plates extending perpendicularlyto the axis of the boiler and attached at one end to the reentrantbottom and at the other end to the exterior boiler shell, and diagonalbraces ex tending between said tie plates.

1. A boiler crescent shaped in cross section to form opposedlongitudinally extending water legs, said boiler having a ren trantbottom forming an inverted U-shaped flue, a tie bar located at one endof the boiler and connecting the extremities of the water legs, and aplurality of tie bars attached to the bottom of the boiler and extendingupward and attached to the top or crown of the boiler.

5. A boiler crescent shaped in cross section to form opposedlongitudinally ext-end ing water legs, said boiler having a reentrantbottom forming an inverted U-shaped flue, tie plates disposed in thewater legs and extending between the reentrant bottom and the exteriorboiler shell, tie bars depending from the crown of the boiler shell andconnected to the rentrant bottom, and a transversely extending tie bardisposed at one end of the boiler and extending between the water legsthereof for holding said water legs from spreading.

6. A boiler crescent shaped in cross section to form opposedlongitudinally extending water legs and having a reentrant bottomforming an inverted U-shaped flue, tie plates disposed in the lowerportions of the water legs and extending perpendicularly to the axis ofthe boiler, said tie plates being attached at their opposite ends to thereentrant bottom and to the exterior boiler shell, diagonally arrangedbraces attached at opposite ends to adjacent tie plates and extendingbetween the same, a plurality of vertically disposed tie rods, eachattached at its upper end to the crown of the boiler and at its lowerend to the rentrant bottom thereof, a transversely extending tie barlocated at one end of the boiler and connecting the lower ends of thewater legs.

7. A boiler crescent shaped in cross section to form opposedlongitudinally extending water legs, said boiler having a reentrantbottom forming an inverted U-shaped flue, a plurality of transverselyextending angle irons attached to the inner face of the rentrant bottom,a plurality of tie rods attached at their upper ends to the crown of theboiler and at their lower ends attached to the angle irons, and tieplates disposed near the ends of the legs of the boiler and extendingperpendicularly to the axis of the boiler, said tie plates beingconnected at their inner ends to the angle irons and at their outer endsto the outer shell of the boiler. V

8. A boiler crescent shaped in cross section to form opposedlongitudinally extending water legs, a tie bar extending between thelower ends of the water legs, and tubular bolts"passing through the tiebar and into the boiler at the lower ends of said legs, the tubularbolts being closed by removable plugs.

In testimony whereof, I affix my signature in presence of two witnesses.

JOHN M. CAMERON. [1 s.] Witnesses:

THOS. 0. Cox,

A. F. Hoss.

Copies of this patent may be obtained for five cents each, by addressingthe "Commissioner of Patents, Washington, D. G

